Objective:
Objective 1: Evaluate known resistance-associated maize genes to determine their effects on insects and associated mycotoxigenic fungi, as well as toxin production. Subobjective 1A. Select and clone candidate resistance genes. Subobjective 1B. Express candidate resistance genes in maize callus and evaluate for effects on insects and mycotoxigenic fungi. Subobjective 1C. Express the best candidates identified in Subobjective 1B in regenerated plants and evaluate for insect and fungal resistance.
Objective 2: Use RNA interference to control the regulation of mycotoxins in maize, identify novel genetic mechanisms that may reduce mycotoxin levels produced by Fusarium fungus species, and develop novel strategies to help breeders use the genes. Subobjective 2A. Develop RNA interference expression vectors to reduce DON production in Fusarium graminearum and fumonisin production in F. verticillioides. Subobjective 2B. Transform maize to express optimal RNAi constructs for reduced mycotoxin levels, and evaluate for reduced levels of mycotoxins in inoculated ears.

Approach:
Utilize comparisons with genes of known functionality where possible to narrow the number of potential corn resistance gene candidates down for insect and fungal resistance gene product functionality analysis. Express candidate genes likely to function in corn callus tissue, and evaluate the callus for resistance to insect feeding, fungal growth, and mycotoxin production. Candidate genes whose products have activity against both insects and fungi will be introduced transgenically into corn kernel embryos and the plants will be regenerated and evaluated for resistance to insects and fungi. Additionally, genes acting by RNA interference will be designed to reduce mycotoxin production by Fusarium species, introduced into the fungi, and evaluated for their ability to inhibit mycotoxin production in culture. The most effective examples will be transgenically expressed in corn plants, and ears will be inoculated with Fusarium mycotoxin producers to determine if the presence of these genes will reduce mycotoxin levels.